Device for sampling a pressurised fluid, equipped with means for increasing the volume of the sampling chamber

ABSTRACT

A device for sampling a fluid, includes a sampling chamber including a first piston driven by the fluid, and an additional device configured to increase the volume of the sampling chamber. The sampling chamber serves as both a sampler and also as a container for the sampled fluid and it can also be used as a cell for the analysis of the fluid.

The invention relates to the technical field of exploration andexploitation of underground environment, such as the operation of gasreservoirs (gas storage/withdrawal, exploitation of conventional orunconventional gas or hydrocarbons) and monitoring of these operations(contamination of operations on aquifers). The invention relates inparticular to the field of monitoring of geological sites comprising oilor gas hydrocarbons.

In particular, the invention relates to fluid sampling devices, and moreparticularly to a device for sampling fluids under pressure in a well, apipe, a tube, a duct, a reservoir or the like.

Fluids present in underground environments need to be sampled via wellsto determine their composition, in order to characterize the geologicalreservoirs affected by these wells and their evolution over time duringthe industrial process of storage and/or production.

To implement these methods, it is therefore necessary to have a devicefor taking fluids under pressure in a well drilled through a geologicalformation. Such a device is called sampler or withdrawer.

FTS (Flow Through Sampler) samplers are known, making it possible toobtain fluid samples from a well drilled through a geological formation.Such a device consists of a sample chamber with a spring-loaded valve ateach end. A locking mechanism connects the valves and keeps them opentogether. Above the chamber, there is a clock to program the closingtime, and a triggering mechanism to release the valves. The lower endincludes means for allowing the fluid to penetrate. At the top, there isa cable grip for attaching a cable.

U.S. Pat. No. 5,945,611 discloses a device for taking fluids underpressure in a pipe, a pipe, a duct or the like. The device comprises aplurality of pistons, a body having a common passage, in which saidpistons are slidably mounted, a side inlet port and a side exit portlocated within said passage and communicating with the pipeline, saidinlet and outlet ports located such that movement of the pistons maycover and uncover said inlet and outlet ports.

U.S. Pat. No. 5,896,926 discloses a device for in situ samplingunderground aquifer fluids under static conditions without disturbingthe surroundings but comprising a “packer” for isolating the samplingsystem with the zone located above it, and an in-situ pumping systemlocated within said sampler to “suck” the fluid into the samplingchamber.

Also known from French patent application FR 2999224 (WO 2014/087061) isa sampling device comprising, on the one hand, a piston controlled by aspring bathing in an oil chamber for sampling the fluid and, on theother hand, a second piston for expelling the fluid during transfer. Thedevice is held in the open or closed position by the compressed springhoused in the oil-filled chamber. The oil contained in the chamber ofthe spring makes it possible to damp the decompression effect and tocarry out the sampling without jerk. The device allows the recovery ofthe sampled fluid thanks to the mechanical action of a solid pistonthrough a manual valve. This device also has the advantage of being ableto be lowered in the open position in the underground environment, inorder to allow a complete filling of the sampling chamber.

In order to recover the sampled fluid and to transport the sample to beanalyzed, these sampling devices require the use of means for extractingthe fluid from the sampling chamber and for conditioning the fluid drawnin a dedicated container. These means are complex, may alter thecollected fluid (leakage, pollution of the fluid . . . ) and requiremanipulations.

The invention relates to a device for sampling a fluid comprising asampling chamber comprising a first piston driven by the fluid andadditional means for increasing the volume of the sampling chamber so asto adjust the pressure in the Sampling chamber. Thus, the samplingchamber serves as a sampler but also as a container for the withdrawnfluid and may also serve as a cell for fluid analysis.

The invention relates to a device for sampling at least one pressurizedfluid comprising at least one sampling chamber comprising an internalvolume for receiving said fluid, said sampling chamber comprising afirst piston adapted to be displaced by said fluid. Said samplingchamber comprises additional means for increasing the volume of thesampling chamber.

According to the invention, said sampling chamber is a transportcontainer for said fluid.

According to one embodiment of the invention, said additional means forincreasing the volume of said sampling chamber comprise a compensatingpiston serving as a stop for said first piston and means for adjustingthe position of said compensation piston.

According to one feature of the invention, the means for adjusting theposition of said compensation piston are hydraulic means.

According to one aspect of the invention, said compensating piston has astroke representing between 0.1 and 20% of the volume of sampled fluid.

Advantageously, said sampling device comprises a lower chamber disposedbelow said sampling chamber and has in the lower part of said samplingchamber a fitting for removably fixing said sampling chamber and saidlower chamber, said fitting comprising means for passing a fluid betweensaid sampling chamber and said lower chamber.

Preferably, said compensation piston essentially slides within thefitting around an inner cylinder.

In addition, said sampling device may include a sampling actuationsystem for opening or closing said sampling chamber.

According to an alternative embodiment of the invention, said actuatingsystem comprises motorization means opening and closing said samplingchamber and electronic or mechanical control means of said motorizationmeans.

Advantageously, said electronic control means comprise a clock and/orcommunication means and/or at least one temperature sensor and/or atleast one pressure sensor and/or at least one CCL sensor and/or at leastone gamma ray sensor.

According to one feature of the invention, said sampling chamber isfixed in a removable manner, below said actuating system.

According to one aspect of the invention, said sampling chamber has anupper valve for allowing or inhibiting the passage of said fluid intosaid sampling chamber, said upper valve being arranged above the firstpiston.

Advantageously, said sampling device comprises from one to five samplingchambers, preferably from one to three sampling chambers. In addition,the invention relates to the use of a device according to the inventionfor producing a sample of a fluid in an underground formation. For thisuse, the following steps are carried out:

-   -   a) said sampling device is lowered with said sampling chamber        closed in said underground formation;    -   b) withdrawing said fluid from said sampling chamber of the        sampling device by opening said sampling chamber for a        predetermined time;    -   c) pulling said sampling device to the surface with said        sampling chamber closed; and    -   d) recovering said closed sample chamber containing said fluid        as a sample of said fluid.

Advantageously, during the sampling step, the compensation piston isheld in an upper position, and in the recovery step of the samplingchamber, the compensation piston is lowered in a lower position.

Preferably, said fluid is conveyed within the closed sampling chamber.

According to one aspect of the invention, it is carried out a furtherstep of analyzing said fluid contained in said sampling chamber.

According to an alternate embodiment of the invention, before theanalyzing step, it is carried out a further step of conditioning saidsampling chamber substantially at the temperature and pressureconditions of said underground formation.

Advantageously, said sample is taken for the monitoring of a CO2 storagesite, a site for exploring or exploiting conventional ornon-conventional hydrocarbons, or a geothermal site.

Other characteristics and advantages of the device according to theinvention will appear on reading the following description ofnon-limiting examples of embodiments, with reference to the accompanyingdrawings and described hereinafter.

FIG. 1 illustrates the sampling device according to the invention beforethe fluid is sampled.

FIG. 2 illustrates the sampling chamber and the lower chamber of thesampling device according to the invention before the fluid is sampled.

FIG. 3 illustrates the sampling chamber and the lower chamber of thesampling device according to the invention after the fluid has beensampled.

FIG. 4 illustrates the sampling chamber of the sampling device accordingto the invention after the fluid has been sampled.

FIG. 5 illustrates the sampling chamber of the sampling device accordingto the invention for the transport of the fluid.

FIG. 6 illustrates the intermediate connection of the sampling deviceaccording to the invention.

FIG. 7 illustrates the sampling chamber of the sampling device accordingto the invention equipped with covers for transporting the fluid.

The present invention relates to a device for sampling at least onepressurized fluid, also called a sampler.

The sampler according to the invention comprises at least one samplingchamber defining an internal volume for receiving the fluid to besampled. During sampling, the sampling chamber is filled with the fluidto be sampled. Then, when the sampling is complete, i.e. during theascent of the sampler to the surface, or during the transport of thefluid, the sampled fluid is contained within this sampling chamber. Thesampler according to the invention further comprises additional meansfor increasing the volume of the sampling chamber so as to adjust thepressure in the sampling chamber. The additional means for increasingthe volume of the sampling chamber make it possible to reduce thepressure in the sampling chamber (in the case of a compressible fluid)or to create a gas cap above the fluid (in the case of an incompressiblefluid), in particular when the sampling chamber comprises the fluid tobe sampled. These additional means make it possible to limit the risksassociated with the transport of pressurized equipment; thus, it is nolonger necessary to extract the sampled fluid for its analysis, whichmakes it possible to use the sampling chamber as a container fortransporting the sampled fluid (sampled fluid transporting bottle).

In addition, the sampler may comprise the following means, alone or incombination:

-   -   A system for actuating the sample, which opens and closes the        sampler, so as to allow or prevent the introduction within the        sampler of the fluid to be sampled from the outside environment.        The actuating system is preferably located above the sampling        chamber.    -   A lower chamber, preferably located below the sampling chamber.        The lower chamber communicates with the sampling chamber so as        to allow fluid transfer between the sampling chamber and the        lower chamber.    -   Means for attaching a cable, the cable making it possible to        lower and pull up the sampler in a well or a pipe, a tube, a        conduit, a tank, etc.

The sampling chamber is formed by a cylindrical envelope in which afirst piston moves. The first piston is displaced by the sampled fluid:the pressure of the sampled fluid causes the first piston to move down.The sampled fluid is therefore contained within in the cylindricalenvelope between the upper part of the sampling chamber and the firstpiston.

According to one embodiment of the invention, the additional means forincreasing the volume of the sampling chamber comprise a compensationpiston and means for adjusting the position of the compensation piston.In a lower position of the first piston, i.e. at the end of the samplingand during the transport of the sampler, the first piston is in abutmentagainst a compensating piston. The compensating piston is controlled byadjustment means so as to vary the pressure within the sampling chamber.The means for adjusting the position of the compensating piston positionthe compensating piston in the upper position during sampling and duringpulling the sampler to the surface. The means for adjusting the positionof the compensating piston position the compensation piston in the lowerposition for the transport of the sample. With the first piston abuttingthe compensating piston, and in view of the pressure of the fluid drawnin the sampling chamber, the lowering of the compensation piston causesthe first piston to be lowered.

According to one embodiment of the invention, during the preparationprior to descent, a fluid, for example oil, is injected under thecompensation piston until it protrudes, for example of approximately 15mm, which makes it possible to create an (oil) buffer on which the firstpiston comes to rest when it is in abutment with the compensatingpiston. Once the tool has been brought up to the surface, this (oil)buffer is evacuated, allowing the sample to be transported to thelaboratory at a pressure less than that of the sampling, or even zero(all depends on the quantity of dissolved gas recovered by the sampler.Thus, the internal volume containing the sampled fluid increases, whichmakes it possible to reduce the pressure in the sampling chamber (in thecase of a compressible fluid) or to create a gas cap above the fluid (inthe case of an incompressible fluid). Preferably, this layer of gas orgas cap has a small volume with respect to the volume of the samplingchamber. For this purpose, the stroke of the compensating piston mayrepresent between 0.1% and 25% of the sampled volume, or even more,preferably between 0.1 and 20% of the sampled volume withdrawn. Thisadjustment of the pressure makes it possible to limit the risksassociated with the transport of a pressurized equipment; it istherefore no longer necessary to extract the sampled fluid for itsanalysis, which makes it possible to use the sampling chamber as atransport container for the sampled fluid and as a PVT cell since it ispossible to put the sample back to the underground conditions.

According to one embodiment of the invention, the position of thecompensation piston may be regulated by hydraulic means; the piston ismoved by injecting and withdrawing oil.

According to one embodiment of the invention, a system for actuating thesample allows the opening and closing of the sampler. The actuatingsystem may be comprised in a cylindrical envelope. Preferably, thisopening and this closure are achieved by a valve, called upper valve,located above the first piston. The upper valve is driven by theactuating system, when the sampler is in the desired position in thewell for sampling. The actuating system comprises motorization means, inparticular at least one electric motor capable of driving the uppervalve. The actuating system further comprises means for controlling themotorization means. The control means control the motorization meanswhen the sampler is in the desired position. The control means may bemechanical control means operated from the surface by a user.Alternatively, the control means may be electronic. The electroniccontrol means may comprise means for real-time communication with meanslocated at the surface so as to inform the user of the conditions withinthe well. According to a first alternate embodiment, the electroniccontrol means may comprise an automatic clock, which will trigger thecontrol of the motorization means at a predetermined instant. Accordingto a second alternate embodiment, the control means and the informationreturned in real time can enable the specialist to trigger the samplingonce the position of the sampler in the well has been determined. Thecontrol means may comprise one or more sensors to determine the positionof the sampler in the well. The sensors integrated in the control meansmay comprise one or more temperature sensors, one or more pressuresensors, one or more CCL sensors (Casing Collar Locator, this typesensor allowing to determine the position of the casing joints in awell), one or more gamma ray sensors, etc. Alternatively, these twoalternate embodiments may be associated, and an automatic clockmechanism may be coupled to different sensors. In order to withstandhigh temperature and high pressure conditions, the electronic controlmeans may be integrated into a Dewar vase type heat shield which is acontainer designed to provide very good thermal insulation. This tubemay be in the form of a double-layer glass or metal container. It may beregarded as two thin-walled containers intertwined with one another. Thenarrow space between these two containers is almost entirely devoid ofair, and the near vacuum prevents conduction and convection of heat. Inaddition, the pressure sensor may be a Quatzdyne sensor or equivalent,which is a high-precision sensor and may withstand temperatures up to200° C.

According to one embodiment of the invention, the sampling chamber isreleasably secured, for example by a threaded connection, to theactuating system in order to be able to isolate the sampling chamber, toform a transport container.

According to one embodiment of the invention, the lower chamber is incommunication with the sampling chamber. The lower chamber may becomprised in a cylindrical envelope. The outer diameter of the lowerchamber may be substantially the same as the outer diameter of thesampling chamber, for example by a threaded connection. According to oneembodiment of the invention, the lower chamber is in communication withthe sampling chamber by means of a fitting, called intermediate fitting.The fitting allows the lower chamber and the sampling chamber to befixed in a removable manner. Thus, the sampling chamber may be isolatedfrom the lower chamber to form a transport container.

The fitting includes means for passing a fluid from the sampling chamberto the lower chamber. The fluid passing means prevent the passage of thefluid in the opposite direction from the lower chamber to the samplingchamber. The fluid passing means may comprise a lower cylinder, a nozzlescrew, and a valve system. Advantageously, the lower chamber has avolume greater than the volume of the sampling chamber so as to enablecomplete transfer of the fluid initially contained in the samplingchamber to the lower chamber. Furthermore, the assembly may beconstituted in such a way as to ensure a slow passage of the transferfluid, which makes it possible to ensure that the PVT (pressure, volume,temperature) characteristics of the underground fluid are not changed.

The compensation piston is movable with respect to the fitting.Preferably, the compensation piston is movable essentially within thefitting, so that in a lower position the compensating piston does notprotrude from the fitting whereas in the upper position the compensatingpiston protrudes with respect to the fitting. The height of theprotrusion substantially corresponds to the stroke of the compensatingpiston.

FIG. 1 illustrates the sampling device prior to sampling the fluid,according to a non-limiting embodiment of the invention. The samplingdevice is substantially cylindrical in shape and comprises, from top tobottom, three compartments: a control compartment 20 comprising anactuating system, a sampling chamber 3 and a lower chamber 13.

The illustrated control compartment 20 comprises, in a non-limitingmanner:

-   -   an electric motor 19 for starting or stopping the sampling,    -   a control axis 18 transmitting the movement of the electric        motor 19,    -   a lower tip 21 of the control compartment 20 closing the lower        part of the control compartment 20,    -   an engine cradle 22 for supporting the electric motor 19,    -   an upper tip 23 of the control compartment 20 closing the upper        part of the control compartment 20,    -   a watertight passage 24, in particular for electric cables,    -   a fitting 25 of the control compartment 20 with control means        (not shown), for example electronic or mechanical control means,        and    -   a fitting 17 of the control compartment 20 with the sampling        chamber 3, in order to detachably fix the control compartment 20        to the sampling chamber 3.

The illustrated sampling chamber 3 includes in a non-limiting manner:

-   -   an upper valve 1 for opening or closing the sampling chamber,        that is to say to enable or to prevent the filling of the        sampling chamber 3; the upper valve 1 is driven by the actuating        system, in particular by the motorization means 19; when the        upper valve 1 is open, the fluid penetrates laterally through        openings (oblong in the illustrated embodiment) provided in the        body of the sampler (above the upper valve 1), passes through        the upper valve 1 and penetrates in the sampling chamber 3,    -   an upper tip 2 of the sampler closing the upper part of the        sampling chamber 3 with the upper valve 1,    -   a first piston 4, which is in an upper position before the fluid        is sampled, is pressed onto upper tip 2 and therefore emptying        the space between the first piston 4 and the upper tip 2;    -   an intermediate fitting 9, located in the lower part of the        sampling chamber and which makes it possible to fix in a        removable manner the sampling chamber 3 to the lower chamber 13,    -   a compensating piston 5, movable relative to the intermediate        fitting 9, which is an upper position before the fluid is        sampled, by means of a fluid (oil) located between the        compensation piston 5 and the intermediate fitting 9, and    -   a flap 10 fixed to the intermediate fitting 9 and which allows        passage of the fluid from the sampling chamber 3 to the lower        chamber 13.

The illustrated lower chamber 13 comprises, in a non-limiting manner:

-   -   a lower tip 14 of the sampler closing the lower chamber 13,    -   a closed bottom nose 15 which is fixed to the lower tip 14,        which is at the lower end of the sampler, and has a        substantially conical shape, and    -   a lower valve 16 making it possible to empty the lower chamber        13.

Before the fluid is sampled (FIG. 1 and FIG. 2), the first piston 4 ispressed against the upper nozzle 2, the volume of the sampling chamber 3between the first piston 4 and the intermediate fitting 9 comprises afilling fluid, such as oil, and the volume of the lower chamber 13 isempty or comprises air. In the pressed position of the first piston 4 tothe upper tip 2, a substantially conical surface of the protrudingpiston 4 penetrates into a substantially conical hollow surface of theupper tip 2.

During the sampling of the fluid, the fluid enters the sampling chamber3 by the upper valve 1. The sampled fluid exerts a force on the firstpiston 4 which moves down, and the sampled fluid begins to fill thevolume of the sampling chamber 3 between the upper tip 2 and the firstpiston 4. The lowering of the first piston 4 causes a displacement ofthe filling fluid from the sampling chamber 3 to the lower chamber 13through the intermediate fitting 9 and the flap 10.

Once the sampling is complete and the sampler has returned to thesurface (FIG. 3 and FIG. 4), the first piston 4 is in abutment againstthe compensating piston 5 which is in the upper position. The samplingchamber 3 then only includes the sampled fluid. All the filling fluid isthen in the lower chamber 13.

At the surface, the sample is prepared (FIG. 5) by keeping the samplingchamber 3 only, dismantling the control means 20 and the lower chamber13. In order to allow the safe transport of the pressurized fluid, a gaspad is formed within the sampling chamber 3 by lowering the compensationpiston 5, enabling an increase in the volume of the sampling chamber 3.

An example embodiment of the intermediate fitting 9 is illustrated indetail on FIG. 6. This intermediate fitting 9 may be composed of twovalves 7 a and 7 b, equipped with a throttle 27, a drain valve 8, acompensation piston 5, an inner cylinder 6, a nozzle screw 26 and a flap10, which is in turn composed of a body, a spring 28, a ball 12 and acalibration screw 11.

During the preparation prior to descent, a fluid, preferably oil, isinjected under the compensating piston 5 until it protrudes, for exampleby about 15 mm, thereby creating a buffer (of oil) on which the firstpiston 4 comes to bear when the latter is in abutment against thecompensation piston 5. This (oil) buffer, once the sampler has beendrawn to the surface, is disposed of, allowing the sample to betransported to the laboratory at a pressure less than that of thesampling, or even zero (depending on the quantity of dissolved gaswithdrawn by the sampler).

In one embodiment of the invention, the sampler may be prepared, asillustrated on FIG. 1 and FIG. 2, before any descent into a well, bycarrying out the following steps:

-   -   Step 1: vacuum is created above the first piston 4, for example        by connecting the inlet of the upper valve 1 to a vacuum pump;        in this way, the first piston 4 is pressed against the upper tip        2.    -   Step 2: the compensation piston 5 is put in its upper position,        by carrying out the following steps:        -   The drain screw 8 is unscrewed and then becomes a filling            screw, and the drain screw 8 is replaced by a hose which            dips into an oil container.        -   The valve 7 a is unscrewed, and replaced by a hose connected            to the lower part of an oil container, and in an upper part            of this container, a hose is connected to a pump capable of            making vacuum or pressure.        -   Vacuum is first created in the intermediate fitting 9 and            then the valve 7 b is opened, which sucks the oil through            the filling hose and fills the volume under the compensation            piston 5. Once this volume is filled, the valve 7 b is            closed and the vacuum pump is stopped.        -   The compensation piston 5 is then pushed by injecting oil            under pressure, for which purpose the valve 7 b is closed;            the oil hose may then be disconnected and replaced by the            drain screw 8, the pressure pump is connected to the oil            container and the compensating piston 5 is moved out of the            desired distance (e.g. 15 mm); the injection is then            stopped, the oil hose is disconnected and the valve 7 a is            screwed back. Air contained under the compensation piston 5            is then evacuated and an oil buffer is created under the            compensating piston 5.    -   Step 3: the volume of the sampling chamber 3 is filled with oil        under the piston 4.    -   Step 4: the whole intermediate connection 9 is screwed into the        sampling chamber 3.    -   Step 5: the lower chamber 13 is screwed onto the intermediate        connection 9.    -   Step 6: the lower tip 14 is screwed with its valve 16 on the        lower part of the lower chamber 13.    -   Step 7: vacuum is made in the lower chamber 13, for example by        means of a vacuum pump connected to the lower valve 16.    -   Step 8: the lower nose 15 is fixed to the lower tip 14 of the        sampler.    -   Step 9: the whole control compartment 20 is placed and fixed on        the sampler via the fitting 17 of the control compartment 20 to        the sampling chamber 3.

According to one embodiment of the invention and as illustrated on FIG.3 (on which the control compartment is not shown), at the desired depth,the opening of the upper valve 1 is triggered via the Electric motor 19.The pressure exerted on the upper part of the piston 4 by the fluid tobe sampled causes the piston 4 to move, whereby the oil contained underthe piston 4 is transferred from the sampling chamber 3 to the lowerchamber 13 via a nozzle created in the nozzle screw 26 and contained inthe flap 10.

The function of the flap 10 equipped with its ball 12, slightlycalibrated by the calibration screw 11 which presses the spring 28, isdouble: first, it prevents the transfer of oil by gravity when thesampler is lowered; secondly it opens to compensate for the expansion ofthe volume of oil created by the raising of the oil temperature duringthe descent.

When the piston 4 comes into abutment with the compensation piston 5,the latter compresses the small volume of oil injected before thedescent, and, once the balance of the pressures has been established,stops movement of the piston 4.

After a predetermined time, the upper valve 1 is then closed via theelectric motor 19 and the sampler may be drawn up.

According to one embodiment illustrated on FIG. 4, FIG. 5 and FIG. 7, inorder to form the transport container for the sample, when the sampleris drawn to the surface, the cable head is first disconnected from theelectronic compartment. Then, the electronic compartment of the controlcompartment is disassembled. Then, the sampling assembly (samplingchamber and lower chamber) from the is disconnected from the controlhead assembly.

According to an alternate embodiment, a verification of the sampledvolume may be carried out after this disassembly. For example,verification may involve weighing the complete sampler prior to descentand after the ascent, the difference in weight indicating whether thesampler is full or not.

The pressure in the sampler chamber 3 of the sampler may represent ahazard. In order to limit the risks associated with the transport ofpressurized equipment, it is possible to substantially reduce thispressure by creating a gas cap.

On the one hand, the gas cap is achieved by adjusting the position ofthe compensation piston 5, bringing it into its lower position. Sincethe compensation piston 5 is pushed by the first piston 4, the pressurein the oil chamber is equal, for example, to three times the pressure inthe upper chamber of the sampler, in view of the ratio of the surfacesof the first piston 4 and the compensation piston 5.

On the other hand, the gas cap may be achieved by the temperaturedifference. Indeed, the final pressure contained in the sampler isinfluenced by the final temperature. This temperature has an influenceon both the oil and the sampled liquid. Since the volume of the lowerchamber 13 is greater than that of the sampling chamber 3, the oilcontained in the lower chamber 13 represents no risk. Moreover, a sampletaken at a high temperature (for example 200° C.) is no longer at thistemperature once the sampler has been drawn to the surface; the finalpressure of the fluid at the surface is therefore no longer the same asthat of the bottom, which is safe.

According to one embodiment, in order to reduce the pressure inside thesampler, the following steps may be carried out:

-   -   Step 1: the lower chamber 13 of the intermediate fitting 9 is        unscrewed to check whether the oil transfer is complete or not        (FIG. 4).    -   Step 2: the drain screw 8 of the intermediate fitting 9 is        disassembled and replaced by a drain hose connected to a        drainage container.    -   Step 3: the valve 7 b of the intermediate fitting 9 is        unscrewed, the first piston 4 is then free to push back the        compensation piston 5, which makes it possible to drain the        volume of oil injected before the descent between the        compensation piston 5 and the intermediate fitting 9 (FIG. 5).    -   Step 4: the flap 10 is unscrewed from the intermediate fitting        9.    -   Step 5: a lower cover 29 is screwed onto the intermediate        fitting 9 to replace the lower chamber 13, as well as an upper        protective cover 30 for protection of the upper valve 1 (FIG.        7). The sampler is then conditioned for its transport, in        particular for shipment to an analysis laboratory.

In an alternate embodiment, the sampler comprises several samplingchambers. For example, the sampler may comprise two or three samplingchambers. According to one embodiment of the invention, severalassemblies comprising an actuating system, an upper valve, a samplingchamber and a lower chamber are assembled one below the other. Such asampler allows for several consecutive samplings to be achieved atdifferent depths, without having to draw to the surface the samplerbetween the samplings.

The sampler according to the invention is particularly suitable forsampling fluids in deep wells, for example greater than 3000 m, underhigh pressure and high temperature conditions. The sampler according tothe invention may be provided for sampling a fluid in pressures up to650 bars and more and at temperatures close to 200° C. and higher.

The sampler according to the invention may be used in the field ofmonitoring a CO₂ storage site, a geothermal site, a site for exploringor exploiting hydrocarbons, oils or gases, conventional ornon-conventional, for example for a shale gas site.

The invention also relates to the use of a sampling device for producinga fluid sample in an underground environment, in which the followingsteps are carried out:

-   -   a) The sampling device, with the sampling chamber 3 closed, is        lowered into a well (or a pipe, a duct, a reservoir, etc.) of        the underground environment, in particular by means of a cable        fixed on the actuation system of the sampler;    -   b) When the sampler is at the predetermined position (detected        by mechanical or electronic means), the fluid is withdrawn into        the sampling chamber 3 of the sampling device by opening the        sampling chamber 3, for example by means of the actuation means        which actuates the opening of the upper valve 1;    -   c) Drawing the sampling device to the surface with the sampling        chamber 3 closed, in particular by means of a cable; and    -   d) collecting the sample chamber 3 containing the fluid as a        transport container; for example, according to one embodiment of        the invention, the sampling chamber 3 is separated from the        drive system and from the lower chamber 13, and a gas cap is        generated in the sampling chamber.

The collection of the sampling chamber as a transport container makes itpossible to avoid any extraction and reconditioning of the sampledfluid, which may be a source of deterioration thereof: leakage,pollution . . . .

The gas cap is achieved by adjusting the position of the compensationpiston. For example, the gas cap may be achieved by maintaining thecompensation piston in the upper position during the steps of descent,sampling and ascent, and by lowering the compensation piston in thelower position during the recovery step.

The use of the device according to the invention may also comprise astep of analyzing the sampled fluid. The sampled fluid is transported,in the sampling chamber, from the sampling site to the analysislaboratory. Prior to this analysis step, it is possible to condition thesampling chamber substantially under the conditions of temperature andpressure of the underground environment. Thus, the sampling chamber ofthe sampler is used for sampling, as a transport container and as a PVT(pressure, volume, temperature) analysis cell.

In the description and in the drawings, the following reference signsare used:

-   -   1 upper valve    -   2 upper tip of sampler    -   3 sampling chamber    -   4 first piston    -   5 compensation piston    -   6 inner cylinder    -   7 a, valves    -   7 b    -   8 drain valve    -   9 intermediate fitting    -   10 flap    -   11 valve calibration screw    -   12 flap ball    -   13 lower chamber    -   14 lower tip of the sampler    -   15 bottom nose    -   16 lower valve    -   17 fitting sampler/control compartment    -   18 control axis    -   19 electric motor    -   20 control compartment    -   21 lower tip of control compartment    -   22 engine cradle    -   23 upper tip of the control compartment    -   24 watertight passage    -   25 fitting control compartment/electronic control means    -   26 nozzle screw    -   27 throttle valve    -   28 valve spring    -   29 upper transport cover    -   30 lower transport cover

1. A device for sampling at least one pressurized fluid, comprising atleast one sampling chamber including an inner volume for receiving saidfluid, said sampling chamber comprising a first piston capable of beingdisplaced by said fluid, wherein the sampling chamber comprises anadditional device configured to increase the volume of the samplingchamber.
 2. The device according to claim 1, wherein said samplingchamber is a container for transporting said fluid.
 3. The deviceaccording to claim 1, wherein said additional device configured toincrease the volume of said sampling chamber comprises a compensationpiston serving as a stop for said first piston and a system configuredto adjust a position of said compensation piston.
 4. The deviceaccording to claim 3, wherein the a system configured to adjust theposition of said compensation piston is a hydraulic system.
 5. Thedevice according to claim 3, wherein said compensation piston has astroke representing between 0.1 and 20% of the volume of the sampledfluid.
 6. The device according to claim 1, further comprising a lowerchamber located below said sampling chamber, and, in a lower part ofsaid sampling chamber, a fitting for releasably securing said samplingchamber to said lower chamber, said fitting having a system configuredto pass fluid between said sampling chamber and said lower chamber. 7.The device according to claim 6, wherein said additional deviceconfigured to increase the volume of said sampling chamber comprises acompensation piston serving as a stop for said first piston and a systemconfigured to adjust a position of said compensation piston, and whereinthe compensation piston slides within said fitting around an innercylinder.
 8. The device according to claim 1, wherein said samplingdevice comprises a sampling actuation system for opening or closing saidsampling chamber.
 9. The device according to claim 8, wherein saidactuating system comprises a motor opening and closing said samplingchamber and an electronic or mechanical control system of said motor.10. The device according to claim 9, wherein said electronic controlsystem comprises at least one of the following: a clock, communicationsystem, a temperature sensor, a pressure sensor, a CCL sensor, a gammaray sensor.
 11. The device according to claim 8, wherein said samplingchamber is fixed in a removable manner, below the actuating system. 12.The device according to claim 1, wherein said sampling chamber comprisesan upper valve for allowing or preventing the passage of fluid in saidsampling chamber, said upper valve being disposed above the firstpiston.
 13. The device according to claim 1, wherein said samplingdevice comprises one to five sampling chambers.
 14. A method a forproducing a sample of a fluid in an underground environment with adevice according to claim 1, the method comprising: a) lowering thesampling device in said underground environment with the samplingchamber closed; b) sampling fluid within the sampling chamber of thesampling device by opening the sampling chamber for a predeterminedtime; c) drawing the sampling device to the surface with said samplingchamber closed; d) recovering the closed sampling chamber.
 15. Themethod according to claim 14, wherein, said sampling chamber comprises acompensation piston serving as a stop for said first piston and a systemconfigured to adjust the position of said compensation piston, thecompensation piston is held, during fluid sampling, in an upperposition, and the sampling chamber is, in the recovering step, displacedin a lower position by the compensation piston.
 16. The method accordingto claim 14, wherein the fluid is conveyed while being in the closedsampling chamber.
 17. The method according claim 14, further including astep of analyzing the fluid contained in the sampling chamber.
 18. Themethod according to claim 17, further including, before the analysisstep, a step of conditioning said sampling chamber at the temperatureand pressure conditions of the underground environment.
 19. The methodaccording to claim 14, wherein the sample is taken for monitoring a CO₂storage site, a site for exploring or exploiting conventional orunconventional hydrocarbons, or a geothermal site.